We propose to study the causes of the deleterious effects on human performance of stress or stress-like agents. We have shown previously that introverts are more susceptible to caffeine induced decrements in complex performance tasks (similar to the verbal portion of the Graduate Record Examination) than are extroverts. We plan to 1) extend our previous findings to a broader range of cognitive tasks; 2) develop and cross validate an inventory to identify individuals who as susceptible to the effects of stress like agents; 3) test the generality of the previous findings using other stress-like manipulations (e.g. time pressure); and 4) study the interactive effects on memory retrieval and decision processes of individual differences in stress susceptibility and experimentally induced stress. Specifically, we plan to examine the performance of selected subjects in conditions known to produce decrements from optimal performance. Subjects will serve in both low and high stress conditions and their performance on semantic memory tasks will be examined for evidence of changes in storage procedures, retrieval processes, and decision strategies. We will develop and test theoretical explanations for the impaired performance that some individuals exhibit in stressful situations. The results should prove useful in understanding and alleviating the deleterious effects of stress.